Search Documents

By Richard Hurteau

Design and validation of an integrated guidance system for articulated ground vehicles is investigated. The development of an autonomous industrial vehicle must take into the account the specific geometry of these vehicles; they can be composed of a tractor with 1 or 2 trailers or of articulated type like LHD. Moreover the tractor-trailers type vehicles can have on-axle hitch configuration or positive/negative off axle configuration. The path-tracking of a tractor-trailer vehicle in restricted space is presented and discussed in this paper. Recent results obtained in simulation and validated by experimentation are also presented. These studies can lead to better ways of maneuvering an articulated vehicle in a restricted space or automatically executing of docking and parking maneuvers

May 1, 2002

By Charles Graham

For hundreds of years the standard vertical mine shaft was rectangular shaped and timber lined. There are many advantages to rectangular shafts but as mines became deeper the circular shaft became more popular. The chief advantages of circular, concrete lined shafts are their ability to resist lateral pressure and they offer less resistance to ventilation air. A number of elliptical shafts have been sunk in an attempt to realize the advantages of both the rectangular and the circular shaft. A concrete lined elliptical shaft provides better space utilization than a circular shaft, would allow for shaft sinking with two double drum hoists, as well as concurrent level development. The design also makes one sided stations possible and provides for a simple headframe design.

Feb 1, 2008

By M. Rigaud, N. Zhou, K. Sankaranarayanane, X. Zhou

The effect of amount and type of dispersants on the rheological behaviour of bauxite-based low-cement castables has been studied in detail. The rheological properties: flow resistance and torque viscosity, as measured by a rheometer, are found to be strongly influenced by the amount and type of dispersants. In the present investigation, a mix containing sodium hexametaphosphate, at an optimal level, is observed to be theologically superior at the given experimental conditions.

Jan 1, 2004

By Wencheng Gao

An attractive way to beneficiate magnesium chloride and aluminum chloride is to prepare Mg-Al spinel, an excellent refractory material. Mg4Al2(OH)14?3H2O, the precursor of spinel, can be prepared using a co-precipitate method from aqueous MgCl2-AlCl3 solutions. The co-precipitation process of magnesium-aluminum from acidified chloride solutions by using NaOH or NH4OH as base neutralization agent was studied. Co-precipitation was conducted from different mixed solutions ? at initial CAl=0.0625M and Mg/Al molar ratio from 0.5 to 10, the temperature range from 30 to 90 °C. The effect of other parameters, including base type, method of base addition, base addition rate, aging time, background electrolyte and concentration were also investigated. The co-precipitation process was monitored by potentionmetric(pH) measurements. The experimental pH curves were characterized by two platforms separated by a steep jump in pH at Mg/Al molar ratio 0.5~6. The first platform was centered at about a pH of 3.8 and the pH of second platform was varied with different conditions. When the Mg/Al molar ratio was up to 6~10, the first platform in pH was almost disappeared. Furthermore, the shapes of pH curves were also affected by base type, base addition rate and method of base addition. Experimental results showed that the first platform in pH was connected with Al precipitation, and the second platform was involved with Mg. The final co-precipitates were characterized by XRD, TGA-DTA, particle size analysis, SEM and TEM. We found both Mg/Al molar ratio and temperature proved to be the key parameters controlling the formation of Mg4Al2(OH)14?3H2O phase. At solution Mg/Al ratio=0.5~4, the main precipitate phase was Bayerite (Al(OH)3) admixed with Mg4Al2(OH)14?3H2O; at Mg/Al ratio=4~6, the main phase was Mg4Al2(OH)14?3H2O admixed with some Mg(OH)2; while from Mg/Al ratio=6~10, the systems were mixtures of Mg(OH)2 and Mg4Al2(OH)14?3H2O.

Oct 1, 2011

By Ross Gilders, Leo Cheung, C. David Desjardins

"For the past twenty years significant progress has been made in bacterial leaching. In fact, a recent article in the Northern Miner has cited that nearly all new copper production is based on bioleaching. The bacteria that play the predominant role in bioleaching is an obligate chemolithoautotroph called thiobacillus ferrooxidans. These bacteria thrive in areas rich in sulphide and prefer low acid media. In the simplest sense, they metabolize sulphide converting it to sulphate either as acid or as soluble metal sulphates. This process is well known because these bacteria generate acid mine water. Over the last five( 5) years, we have been carrying out development work on creating optimum bioleach conditions for the extraction of metals from sulphide rich ores and concentrates. Recently, a study was carried out on a byproduct sulphide concentrate produced in a tin flowsheet developed for the Mt. Pleasant Mine of ADEX Mining Corp. The objective was to determine whether a bioleach process might successfully leach this sulphide material which contains copper, zinc, iron and, what is more important, trace metals such as Indium, Gallium, and Bismuth. The current work describes the successful recovery of these metals achieving extractions of more than 80% by applying bioleaching techniques. An overview of this technical program forms the basis of this paper.IntroductionBio-Oxidation of metal sulphides has emerged to be one of the leading edge hydrometallurgical processes for the economic extraction of metals from ore and concentrates. The fundamental process involves the bacterial assisted oxidation of sulphide to sulphate yielding metal sulphates which can be subsequently leached by conventional means. The bacteria that play the predominate role is an obligate chemolithoautotroph named thiobacillus ferrooxidans (TF). These bacteria thrive in areas rich in sulphide and occur naturally worldwide. In fact, TF is responsible for generating acid in water (acid mine water) from exposed sulphide surfaces primarily through the oxidation of pyrite. TF bacteria thrive under the proper conditions of temperature and oxygen supply in the presence of sulphides and populations in excess of a million per millilitre (ml) of solution are achievable. Typically, at room temperature, the bacteria will bio-oxidize in a pH range of 1.0 to 3.0. Today, bio-oxidation has been applied commercially with great success for the extraction of uranium, copper, and gold."

Jan 1, 1996

By R. W. Pugh, S. L. Ma

"High carbon rods are typically used as the grinding media in rod mills. Usually an AISI I 090 grade of steel is used which provides the high hardness needed for abrasion resistance and sufficient toughness to prevent rod breakage.Work to improve performance in the past has mainly concentrated on increasing the hardness for improved abrasion resistance. This has been accomplished by adding alloys to the steel which uniformly increase the hardness across the rod section.However uniformly increasing the hardness of the rod produces a more brittle product and at high hardness l1evels can lead to rod breakage problems. Heat treatment processes can be used to selectively increase the surface hardness to high levels while maintaining the core at lower hardness levels to give a product that wears slower without breakage. AltaSteel has developed and mill tested a higher hardness heat treated grinding rodThis paper describes the development of a simple model to predict performance improvement with different hardness profiles and the AltaSteel heat-treated grinding rod process. Mill characteristics of the Endako operation are summarized and predicted performance improvements based on hardmess are compared to the approximate 25% achieved in trials running since July, 1991 at this mill. Early results of other mill trials are also presented.INTRODUCTIONAltaSteel, in Edmonton is a major supplier of grinding media. We have a strong desire to continually increase the quality and performance of our products and thereby improve the efficiency of our customers' processes. In the area of grinding rods, we wanted to produce a product with a significant improvement in wear rate. Second to energy, rod consumption usually represents the next highest cost in processing. This paper presents our development of a heattreated grinding rod that has reduced consumption by about 25% in trials to date."

Jan 1, 1993

By A. Fischersworring-Bunk

The new inline six spark-ignition engine is the realization of BMW's concept of efficient dynamics at high technological level to achieve the attributes of low weight and high efficiency, The paper presents different aspects of the development and manufacturing of BMW's inline six-cylinder engine magnesium-aluminium composite crankcase, Reference will be made on the AJ magnesium alloy optimization approach to balance between mechanical properties and the high pressure die cast ability requirements, Next to this aspect some mechanical design issues will be covered, with CAE methods playing an instrumental role in the early project stage for the assessment of the compound concept, Due to the compound design chosen, the interface posed challenges to both design and productions, A set of novel techniques has been used to cope with these tasks.

Jan 1, 2006

By L. Sun

Recently, micro-tubular solid oxide fuel cells (SOFCs) have attracted the attention of many researchers because of their numerous advantages over larger tubular and planar SOFCs. These include excellent thermal shock properties giving rapid startup/shutdown capability, a high volumetric power density compared to larger tubular SOFCs, and reduced sealing problem compared to planar SOFCs. In order to screen cathode materials for micro-tubular SOFCs, the perovskite cathodes were deposited, using a variety of methods, on 10.5 mol % yttria-stabilized zirconia (YSZ) tubes. Their electrochemical properties were then evaluated by using electrochemical impedance spectroscopy and steady-state polarization methods, based on a three electrode configuration, and with the reference electrode position carefully optimized. The oxygen reduction reaction kinetics at the cathode/electrolyte half cell were then investigated in detail.

Jan 1, 2005

By C. Cortés

Flotation is a highly interactive process where a change or disturbance in any part of the circuit results in different final grades and recoveries. This high variability of the circuit metallurgical performance complicates the diagnosis of the scavenger stage at the end of the line, as copper losses in the final tailings are erratic and not totally a consequence of problems in the scavenger section. The assessment of the scavenger performance requires a more elaborated procedure than that used for others stages of the circuit. This communication describes the application of an approach that combines results of laboratory flotation tests with those of surveys performed at the plant. The approach is based on running surveys in one of the circuit lines to collect samples for determining grade vs. recovery curves for total mass and size-by-size fractions. Full mineralogical and liberation analyses are also considered on some samples of the feed and tailings streams selected to have a range of feed grades. A separate sample of the feed is used to run laboratory flotation tests to determine optimum flotation time. Two additional pieces of information are the effect of operating variables on recovery, determined through a test program based on design of experiment techniques, and operational data on every cell in the line gathered by visual observation. The application of this approach to one of the scavenger lines at Los Colorados concentrator (Minera Escondida, BHP Billiton) is demonstrated.

Jan 1, 2007

By W. T. Thompson, S. Durham, K. M. Jaansalu

The role of platinum on the relative stability of gamma - gamma prime equilibrium is only qualitatively known, and may bear upon the stability of a superalloy under a protective coating. The binary phase diagrams Ni-Pt and Al-Pt, and the Ni-rich corner of the Ni-Al-Pt ternary, are reviewed and simple self-consistent thermodynamic models are derived. These thermodynamic models are incorporated into a database used to predict the gamma-gamma prime equilibrium for single crystal superalloys. In small concentrations, platinum is predicted to increase the temperature stability, but not the proportion, of the gamma prime phase over the gamma phase in third generation alloys such as CMSX-10. Another effect of platinum addition is to significantly lower the solidus temperature. These findings are compared to experimental data in the literature.

Jan 1, 2004

By W. M. Silva, Bittencourt. L. R. M.

Three newly developed alumino-silicate refractory bricks for use in safety lining of aluminum electrolysis cells were compared to one commonly used bricks for the same application. It was shown that the increase in silica content and decrease in permeability led to a sensitive decrease in cryolite attack. Both parameters are of utmost importance in selecting bricks for these cells. The reasons for this observation were the formation of a more viscous liquid after the reaction between molten cryolite and the brick, and the reduction of the rate of penetration. Moreover, a novel mortar with high silica content was tested and has shown improved resistance to molten cryolite. The use of oxidizing atmosphere led to increased attack rate in the brick when compared to reducing condition. The opposite effect was observed in the mortars.

Jan 1, 2004

By Joseph J. Poveromo

The blast furnace today continues as the primary production method of hot metal in large-scale steel production. The blast furnace process has been the target of repeated attempts to replace it with various process options, including direct reduction and coke-free smelting reduction. While these new technologies are being adopted in appropriate niches, the blast furnace has responded to the challenge by being amenable to continuous improvement. I will review the role of the blast furnace, major developmental and improvement trends, and then list the current important issues in ironmaking. I will outline the challenges to be faced by the blast furnace to maintain its position as the primary hot metal production process. The material presented here is an update of earlier presentations made in Stockholm, Sweden, 1996, Duluth, 1998 and Chicago, 2000.

May 1, 2003

By A. J. Antony Chettupuzha

During a construction project, it is important to ensure that accurate and pertinent knowledge is delivered on time to appropriate personnel. The criticality of documents exchanged or referred to by various parties, evolves over the course of the project lifecycle. Determining the criticality of documents at different stages of the project can aid companies with managing the flow of information in an organized manner, while providing for the detection of potentially disruptive, erroneous material that could result in delays and costs. Therefore, it is crucial to determine documents which have the potential to disrupt a process (by virtue of being incorrect versions etc.) so that they may be isolated or prevented from entering or interfering with the active flow of information in a project, while also ensuring standard revisions of documents are recognized and accessed accordingly. Electronic Product and Process Management [EPPM] systems provide the capability to establish and map information flow between different parties in a construction project. Analyzing an EPPM system may yield information about the criticality of certain documents within an activity, as well as isolate characteristics peculiar to documents which can assist in risk mitigation. We propose methodology that identifies such critical documents.

Aug 1, 2013

By Serena Biella

Gold has received a growing interest as a catalyst for the selective oxidation of organic molecules using oxygen under mild conditions1. In the liquid phase application small gold particles (2.5-7 nm) deposited over different solid supports can be used but, like many other noble metals, their catalytic activity depends upon the nature of the support and the preparation metod2-5. In particular, gold on carbon is the preferred catalyst for the oxidation of the alcoholic 2-7 and the aldehydic7-9 groups and one of the best preparation method is the immobilisation of colloidal particles2-5,8,9. Suggested application of gold catalysis in fine chemicals production, tested on laboratory scale preparations, is reported in table 110. In order to produce more efficient catalysts for the liquid phase oxidation and to derive new insights into the reaction mechanism, we have made a comparison among catalytic systems based on different metals. The first effort was to test the activity, if present, of naked metal particles and then to study the influence of various materials commonly used as a support.

Oct 1, 2003

By K. Yoo

Chalcopyrite is the most abundant copper sulfide mineral, which is normally processed using pyrometallurgical methods (i.e., smelting) to produce copper metal. Smelting has several major disadvantages, such as high gas-handling costs, high capital costs, saturation of sulfuric acid market, and inability to treat low-grade concentrates and to recover some by-products, such as zinc, nickel and cobalt. The development of hydrometallurgical processes for chalcopyrite is desirable to overcome the problems of smelting. Because chalcopyrite is refractory, the leaching rate for chalcopyrite is very low. Therefore, increasing the leaching rate has been extensively investigated, both in sulfate and chloride media, as well as in the presence of bacteria. Chloride leaching processes have shown relatively high leaching rates. The mechanism of the chloride leaching process has been investigated, but the behavior of chalcopyrite leaching in chloride solution is not clear. Therefore, the effect of the solution redox potential on the leaching rate of chalcopyrite in chloride solution was investigated. In the present study, leaching experiments were carried out using 0.1 M chloride solutions and the results indicate that high leaching rates of chalcopyrite can be achieved at relatively low solution redox potentials.

Jan 1, 2007

By V. Chatain

The environmental assessment of historical mining sites contaminated with various inorganic species, as also the determination of remediation targets require a better knowledge of pollutant-bearing phases. The objective of this paper was to investigate the operational fractionation of arsenic (As) in an As contaminated (ca. 3 wt%) soil collected from a gold mining site in France, where mining activities and smelting processes of gold ores took place until 2004. Single and sequential chemical extraction procedures were performed to evaluate the potential mobility of As according to the fractions to which it was associated in the contaminated soil, and also the part of As sorbed onto soil particles. These procedures used provided information on the nature of As fixation processes in the mining soil studied. Results showed that As appeared mainly sorbed (ca. 72%) with iron on the soil particles, in particular amorphous iron oxyhydroxides. These results confirmed a potential risk of arsenic mobilization under acidic and/or reducing conditions, which frequently occur in mining environment. This research evidenced the importance of the knowledge of As-bearing phases to better predict the mobility of this pollutant and in turn improve the management of As contaminated sites.

Aug 1, 2013

By T. Motegi

Semisolid casting provides grain refinement of the cast structure and prevents macro-segregation. The conventional semisolid slurry is obtained by electromagnetic or mechanical stirring. In our process, the magnesium alloy (AZ31) slurry is made using an inclined cooling plate instead of the conventional methods. The slurry obtained is cast into a twin-roll caster and makes a continuous sheet of 2 or 3 mm thick. The most important factors that influence the sheet casting are the casting temperature and twin-roll speed.

Jan 1, 2007

By T. Takahashi, K. Oyamada, Y. Miyata, T. Isoo

The carbonation reaction of steelmaking slag has been known for many years. However, the size of blocks manufactured from this by-product material has been limited due to the difficulty of achieving a uniform reaction throughout the block. Using newly developed conditions, large porous slag blocks (1.0 x 1.0 x 0.5 m) were produced by car¬bonation of steelmaking slag with the optimum amount of water and supplying CO2 deep into slag powder compacted in molds. The development of these blocks has great poten-tial to solve the problem of slag utilization, for example, by recycling slag in large car¬bonated blocks for artificial fish reefs and seaweed cultivation beds. This paper de¬scribes the carbonation reaction, the new process for producing large slag blocks, and the utilization of blocks in past and recent years.

Jan 1, 2004

By S. K. Sadrnezhaad, B. Hashemi, Z. A. Nemati, Z. Moghimi

Based on the kinetics relationships of a solid - gas model, a software was developed for the prediction of oxidation. Preliminary prediction of oxidation by the software and experimental results of MgO-C refractories were studied and compared. By using the obtained data from this approach, the effective diffusion coefficient, intermolecular diffusion coefficient and diffusion activation energy in the MgO-C refractories, containing various amount of graphite were obtained at different temperatures. First of all, the prediction by the software was very compatible with experimental results, for different oxidation mechanisms in the MgO-C refractories. The results showed that pore diffusion is the predominant oxidation mechanism in this system. The results indicated that when graphite content was above 10wt%, the intermolecular diffusion coefficient was independent from graphite content, and it was closed to a constant value at each temperature.

Jan 1, 2004

By Fengxiang He, T. Meadowcroft, Yanjun Zhang

Slag from the zinc fuming furnaces contains about 3 percent zinc and 0.1 percent lead. The paper outlines several experimental techniques for recovering these components from liquid fumer slag. The simplest method, remelting followed by a hold period, indicated that a substantial fraction of the metal values was recoverable as a result of fuming into the gas phase, presumable by reduction of the metal ions by divalent iron ions. Following on from this, slag samples were equilibrated with copper, chosen because the activity coefficients of zinc and lead in copper are very low. This improved metal recovery, with substantial amounts of lead and zinc reporting to the liquid copper as well as to the fume. Application of an electrical emf across the slag-metal interface, using a graphite anode and a liquid copper cathode, resulted in further gains in metal recovery.

Jan 1, 2004